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At least 217 records · Page 12Linked to original sources
PubMed1983

[Development of fiber type composition and fiber diameter in the longissimus muscle of the domestic pig (Sus scrofa domesticus)].

The development of fiber types composition and fiber diameter in porcine longissimus muscle from birth to the age of 5 years was examined by means of cross-sectional study. The fiber types were classified in the following manner: FTG = fast-twitch-glycolytic, FTO = fast-twitch-oxidative and STO = slow-twitch-oxidative. The percentage on the oxidative fibers decrease from 60.8% on the 1st d to 39.1% on the 100th d of life. On the 1800th d only 26.5% oxidative fibers are present. The average diameters of fiber types increase during the whole examination period, especially to the 100th d of life. The initial gradation of fiber diameter FTG = 63 micron, FTO = 62 micron, STO = 56 micron converts during growth into STO = 112 micron, FTO = 108 micron, FTG = 104 micron. A common representation of muscle fiber diameter growth curve and rump length growth curve demonstrates different growth modes of muscle and skeleton.

Age Factors↗
PubMedDate not supplied

Repeated single fiber recordings do not affect the jitter and the fiber density.

The temporal variation of at least two muscle fibers of the same motor unit was recorded with the single fiber EMG technique (SFEMG) by means of special needles and filter settings. In the normal musculus extensor digitorum communis (EDC) the mean variation (jitter) is not longer than 37 microseconds, the fiber density not higher than 1.7 fibers in a 10 ms window. To determine whether these parameters are affected by repeated SFEMG recordings, we measured jitter and fiber density in 20 fiber pairs in the left extensor digitorum communis muscle on day 0, 3, 6, 9 and 30 in 5 healthy volunteers. The mean jitter and the fiber density did not change significantly from day 0 (30.1 +/- 3.6 microseconds; 1.4 +/- 0.07) to day 30 (34.5 +/- 2.7 microseconds; 1.6 +/- 0.13). We conclude that repeated SFEMG recordings do not influence jitter and fiber density.

Adult↗
PubMed1996

Genesis of newt sperm axial fiber: cDNA cloning and expression of a 29 kDa protein, a major component of the axial fiber, during spermatogenesis.

Newt sperm has a unique structure: the tail consists of axial fiber, undulating membrane and flagellum. The genesis and chemical composition of the axial fiber remain unknown. The axial fiber consists of about 10 major components, as evidenced by SDS-polyacrylamide gel electrophoresis. In order to clarify the biochemical properties of the components of the axial fiber and study the mechanism of axial fiber formation, we focused our attention on a 29 kDa protein, the major constituent of the axial fiber. Immunofluorescent antibody technique showed that the 29 kDa protein was first expressed in the cytoplasm of early round spermatids but was expressed on fibers in the periphery of the cyst in late round spermatids. Double staining with tubulin antibody and 29 kDa antibody showed that the fibers around the cysts in early round spermatids were flagella alone but those in late round spermatids consisted of flagella and 29 kDa protein. These results indicated that 29 kDa proteins are synthesizsed in the cytoplasm of round spermatids and enter the preformed flagella in late round and elongated spermatids. A cDNA clone for 29 kDA protein was isolated. A database search could not find any homologous clones, indicating that the 29 kDa protein is a new one. Northern blot with the cDNA showed that mRNA for 29 kDa protein was highly expressed in round spermatids but barely in primary spermatocytes, indicating that the mRNA for 29 kDa protein is haploid-expressed.

Amino Acid Sequence↗
PubMed1998

Concomitant expression of genes encoding integrin alpha v beta 5 heterodimer and vitronectin in growing parallel fibers of postnatal rat cerebellum: a possible role as mediators of parallel fiber elongation.

External granule cells in the premigratory zone and the upper molecular layer of neonatal rat cerebellum elongate their neurites (parallel fibers) bidirectionally before and during migration into the internal granular layer. In the present study, it is shown that integrin alpha v beta 5 heterodimer (INT alpha v beta 5) is expressed in parallel fibers in these layers at postnatal days 3-20, but not in migrating granule cells or mature parallel fibers. Vitronectin (VN), the dominant ligand for INT alpha v beta 5, was concomitantly detected in the premigratory zone and the upper molecular layer during this period. Several other subunits including alpha 1-6 and beta 1-4 were not detected. When granule cells were prepared from postnatal cerebella and cultured for a few days, the parallel fibers elongated well in response to VN, but the granule cells did not migrate on VN. This fiber elongation was specifically inhibited by both anti-INT alpha v beta 5 antibody and peptides containing Arg-Gly-Asp (RGD), a sequence responsible for cell adhesion mediated by VN. Neither control integrin antibody against integrin alpha v beta 3 heterodimer nor control peptides containing Arg-Gly-Glu (RGE) showed an inhibitory effect on fiber elongation. These observations strongly suggest that the INT alpha v beta 5 VN receptor plays a role in the elongation of parallel fibers from granule cells during cerebellar histogenesis, but its expression is not required for their maintenance or granule cell migration. INT alpha v beta k could be considered as a new marker of parallel fibers during cerebellar development.

Animals↗
PubMed1992

Tissue ablation with excimer laser and multiple fiber catheters: effects of optical fiber density and fluence.

This study was performed to assess the ablational properties of 1.4-, 1.7-, and 2.0-mm wire-guided multiple fiber catheters coupled to a XeCl excimer laser. Samples of postmortem human aorta were irradiated in blood at fluences of 40, 50, and 60 mJ/mm 2. Our results indicate that: 1) an increase in the active irradiation coverage results in an increase in the ablation efficiency; 2) the ablation efficiency is not fluence related using the 1.4- or 1.7-mm multiple fiber catheter but efficiency is fluence dependent using the 2.0-mm multiple fiber catheter; 3) the depth of tissue ablated with a multiple fiber catheter depends primarily upon the proportion of the active irradiation coverage at the catheter tip; 4) the 2.0-mm multiple fiber catheter induces craters surrounded by a larger zone of tissue damage than that observed with the 1.4- or 1.7-mm multiple fiber catheter; and 5) the 2.0-mm multiple fiber catheter should be used cautiously for laser angioplasty because of its high penetration and its risk of arterial wall damage.

Angioplasty, Laser↗
PubMed2001

Congruence of mossy fiber and climbing fiber tactile projections in the lateral hemispheres of the rat cerebellum.

We have examined the spatial relationship between the mossy fiber and climbing fiber projections to crus IIa in the lateral hemispheres of the rat cerebellum. Experiments were performed in ketamine/xylazine anesthetized rats using extracellular recordings and high-density micromapping techniques. Responses were elicited using small, tactile stimuli applied to the perioral and forelimb regions at a rate of 0.5 Hz. In our first series of experiments we demonstrate that the primary (i.e., strongest) receptive field for a single Purkinje cell's complex spike is similar to the primary receptive field of the granule cells immediately subjacent to that Purkinje cell. In our second series of experiments we demonstrate that the granule cell region most strongly activated by a particular peripheral stimulus is immediately subjacent to the Purkinje cells whose complex spikes are also activated most strongly by the same stimulus. The region of climbing fibers activated by a localized peripheral stimulus is "patchy"; it clearly does not conform to the notion of a continuous microzone. These results support original observations first reported in the 1960s using evoked potential recording techniques that the mossy fiber and climbing fiber pathways converge in cerebellar cortex. However, we extend this earlier work to show that the two pathways converge at the level of single Purkinje cells. Many cerebellar theories assume that mossy fiber and climbing fiber pathways carry information from different peripheral locations or different modalities to cerebellar Purkinje cells. Our results appear to contradict this basic assumption for at least the tactile regions of the lateral hemispheres.

Action Potentials↗
PubMed2000

Implications of different fiber measures for epidemiologic studies of man-made vitreous fibers.

BACKGROUND: Several researchers have proposed fiber size ranges representing hypotheses about the biological activity of fibers. Each of these indices has a biologically plausible rationale, yet they propose different fiber dimensions. METHODS: Four biologically based and one standard fiber analytic method index, the NIOSH 7400 method with B rules, were evaluated in air monitoring data collected in a variety of fiber glass (FG) manufacturing settings to determine their impact on an assessment of fiber exposure for an epidemiologic study of the risk of respiratory cancer among FG production workers. RESULTS: All indices varied considerably within and among the range of fiber size distributions sampled in the FG factories. CONCLUSIONS: The asymptotic relative efficiencies (R(2)) calculated among the five indices indicate a potentially important loss of power from the use of the standard method index, if one of the biologically based indices is more closely related to the disease outcome in an epidemiologic study.

Epidemiologic Methods↗
PubMed1988

Development of intersecting CNS fiber tracts: the corpus callosum and its perforating fiber pathway.

What are the mechanisms acting during development at points of intersection of central nervous system fiber tracts which influence the direction taken by a population of growing axons? In order to address this question, the ontogeny of the intersecting rostral corpus callosum and its perforating fiber pathway (PF), and the microenvironment through which these fiber systems grow, were examined in a series of mouse embryos and early postnates. Our results show that the perforating fibers are identifiable in silver-stained sections between embryonic days (E) 15 and 16, at least 1 day prior to the initial appearance of the callosal projection. Soon after the PF can be identified, a dense accumulation of subventricular cells surrounds the PF at a point just ventral to the location where the callosum and PF will intersect (i.e., at the corticoseptal boundary). Callosal axons, which are present at the point of intersection beginning on E17, do not joint the perforating fibers, nor do they appear to penetrate the underlying population of subventricular cells. Instead, the callosal fibers turn across the PF and enter the contralateral cerebral hemisphere. Thus, the intersection of the callosal and perforating fiber systems during development may be related both to the sequential development of each pathway and to the altered nonneuronal environment at the point of intersection.

Animals↗
PubMed1990

Single fiber studies of ascending input to the cuneate nucleus of cats: I. Morphometry of primary afferent fibers.

The morphology of afferent fibers ascending to the cuneate nucleus has been examined in this and the subsequent paper in order to quantify the pattern of arborization and bouton arrangement of selected classes of primary afferents and to compare these data with data from postsynaptic fibers ascending to the cuneate nucleus. Electrophysiologically identified G hair and Ia muscle afferent fibers in the cuneate fasciculus were intraaxonally injected with horseradish peroxidase. Cutaneous afferents terminated dorsal to proprioceptive afferents, especially at middle levels of the cuneate nucleus. The spacing of collaterals along G hair fibers was variable, but averaged 1.46 collaterals per mm; collateral density was higher at middle cuneate levels than in the rest of the nucleus. Collateral density of Ia fibers was lower than for G hair fibers and was lowest at caudal levels of the nucleus. Branches of G hair collaterals, though often initially diverging, usually converged to terminate in a single focus in the dorsal part of the nucleus. The probability of bifurcation of Ia collaterals decreased steadily at successive branch points. These collaterals branched less symmetrically than G hair collaterals, and terminated in the ventral cuneate with less dense arbors, stretched mediolaterally, but of comparable cross-sectional area. Individual G hair collaterals gave rise to more boutons than Ia collaterals; in both cases they were mostly of the en passant type. Boutons were restricted to distal branches of G hair collaterals, whereas boutons of Ia collaterals were also located on proximal branches. Bouton size was similar for the two classes of collaterals. The data reported here, in combination with the published literature, suggest that the collaterals of roughly 300 G hair fibers overlap at any given point at middle levels of the cuneate nucleus. This high degree of anatomical convergence is not predicted by the functional segregation described with electrophysiological mapping, implying the presence of intrinsic nuclear mechanisms enhancing response specificity.

Afferent Pathways↗
PubMed2002

The expression of GABA in mossy fiber synaptosomes coincides with the seizure-induced expression of GABAergic transmission in the mossy fiber synapse.

Although the granule cells of the dentate gyrus are glutamatergic, they contain the machinery for the synthesis and vesiculation of GABA. Furthermore, glutamic acid decarboxylase and the vesicular GABA transporter mRNA are expressed in the granule cells and mossy fibers in an activity-dependent manner, suggesting that these cells release GABA in addition to glutamate. Supporting this hypothesis, we found that seizures induce simultaneous glutamatergic and GABAergic transmission in the mossy fiber projection. To further explore this expression of inhibition, we looked for the presence and expression of endogenous GABA in a synaptosomal preparation enriched with mossy fiber nerve endings of kindled rats. We also studied the capacity of this preparation to capture and release [(3)H]GABA under control conditions and after kindling epilepsy. In accordance with our hypothesis we show that the mossy fiber synaptosomal preparation of the kindled rats has a significantly higher content of endogenous GABA than controls. We also found that the protein content in the mossy fiber synaptosomal preparation of kindled rats was significantly augmented, which is consistent with mossy fiber sprouting. Due to this, the total [(3)H]GABA incorporated in the synaptosomal preparation was also augmented. However, [(3)H]GABA uptake (expressed in % radioactivity/mg protein) and its evoked release were similar in both groups. With the present results, we provide further support for the hypothesis of the emergence of GABAergic transmission in the mossy fiber synapse that can constitute a protective mechanism in response to seizures.

Animals↗
PubMed1995

Tau protein immunoreactivity in muscle fibers with rimmed vacuoles differs from that in regenerating muscle fibers.

To determine whether tau protein found in muscle fibers with rimmed vacuoles and in regenerating fibers was phosphorylated, we examined eight muscle biopsy samples containing rimmed vacuoles (from five patients with distal myopathy with rimmed vacuole formation and three patients with inclusion body myositis) and three muscle biopsy samples from patients with Duchenne muscular dystrophy containing numerous regenerating fibers. Although both rimmed vacuolated and regenerating fibers had increased immunoreactivity against tubulin and tau protein, tau protein in the former was more highly phosphorylated than that in the latter. While very few microtubules in muscle fibers with rimmed vacuoles were recognizable by electron microscopy, regenerating fibers, especially immature ones, contained numerous microtubules. Since tau protein found in vacuolated fibers is hyperphosphorylated, it can be considered to have reduced ability to bind tubulin molecules. Thus, the tau protein cannot stabilize microtubules, resulting in their depolymerization even in the presence of tubulin molecules.

Adolescent↗
PubMed1995

Distribution of galanin-immunoreactive nerve fibers in the carotid labyrinth of the bullfrog, Rana catesbeiana: Comparison with substance P-immunoreactive fibers.

Immunoreactivity of galanin (GAL) was detected in the nerve fibers distributed within the intervascular stroma of the bullfrog carotid labyrinth. GAL-immunoreactive fibers are numerous, and some are close to the sinusoidal plexus. Most GAL fibers appear as thin processes with some varicosities. A combination of indirect double immunofluorescence labelling and image processing clearly demonstrated that the distribution pattern of GAL fibers is different from that of SP fibers. This indicates that GAL and SP do not coexist in the same nerve fibers. The role of GAL fibers may be different from that of previously reported neuropeptides (substance P, calcitonin gene-related peptide, vasoactive intestinal polypeptide, neuropeptide Y, and others) as a neuromodulator in controlling vascular tone of the labyrinth.

Animals↗
PubMed1997

A simple immunofluorescence technique for simultaneous visualization of mast cells and nerve fibers reveals selectivity and hair cycle--dependent changes in mast cell--nerve fiber contacts in murine skin.

Close contacts between mast cells (MC) and nerve fibers have previously been demonstrated in normal and inflamed skin by light and electron microscopy. A key step for any study in MC-nerve interactions in situ is to simultaneously visualize both communication partners, preferably with the option of double labelling the nerve fibers. For this purpose, we developed the following triple-staining technique. After paraformaldehyde-picric acid perfusion fixation, cryostat sections of back skin from C57BL/6 mice were incubated with a primary rat monoclonal antibody to substance P (SP), followed by incubation with a secondary goat-anti-rat TRITC-conjugated IgG. A rabbit antiserum to CGRP was then applied, followed by a secondary goat-anti-rabbit FITC-conjugated IgG. MCs were visualized by incubation with AMCA-labelled avidin, or (for a more convenient quantification of close MC-nerve fiber contacts) with a mixture of TRITC- and FITC-labelled avidins. Using this simple, novel covisualization method, we were able to show that MC-nerve associations in mouse skin are, contrary to previous suggestions, highly selective for nerve fiber types, and that these interactions are regulated in a hair cycle-dependent manner: in telogen and early anagen skin, MCs preferentially contacted CGRP-immunoreactive (IR) or SP/CGRP-IR double-labelled nerve fibers. Compared with telogen values, there was a significant increase in the number of close contacts between MCs and tyrosine hydroxylase-IR fibers during late anagen, and between MCs and peptide histidine-methionine-IR and choline acetyl transferase-IR fibers during catagen.

Adult↗
PubMed1991

Differential blocking action of Joro spider toxin analog on parallel fiber and climbing fiber synapses in cerebellar Purkinje cells.

Synaptic potentials were recorded intracellularly from Purkinje cells in guinea pig cerebellar slices. EPSPs evoked by stimulation of parallel fibers were effectively blocked by perfusion of a slice with the synthetic analog of Joro spider toxin, 1-naphthylacetyl-spermine (NAS) at 250 microM. However, it did not influence those responses evoked by stimulation of climbing fibers. This action of NAS is in contrast to other commonly used glutamate antagonists, CNQX or APV: CNQX (5 microM) blocked both parallel fiber- and climbing fiber-induced responses, while APV (up to 1 mM) did not influence either except for a weak reduction observed in climbing fiber responses. NAS thus provides a useful tool for pharmacologically distinguishing parallel fiber and climbing fiber synapses.

2-Amino-5-phosphonovalerate↗
PubMed2005

Preservation of in vitro muscle fiber function in dermatomyositis and inclusion body myositis: a single fiber study.

Five patients with untreated dermatomyositis, five with inclusion body myositis, and 16 healthy elderly volunteer subjects (controls) underwent open (dermatomyositis and inclusion body myositis) or percutaneous (controls) muscle biopsy. Biopsied muscles included deltoid, biceps and vastus lateralis. Chemically skinned single muscle fibers were activated with Ca(+2); the slack test was performed to determine maximal unloaded shortening velocity (Vo). Parameters measured include single fiber cross sectional area, maximal force, specific force and Vo. 429 Type I and 94 Type IIA fibers were studied. Cross sectional area and maximal force were greater in inclusion body myositis than dermatomyositis or control for Type I and IIA fibers. Specific force of Type I fibers was similar in inclusion body myositis and dermatomyositis but greater than in controls. Vo was greater in Type I, but not IIA, fibers in dermatomyositis compared with inclusion body myositis and controls. The force and velocity generating capacity of single muscle fibers is preserved in patients with dermatomyositis and inclusion body myositis suggesting that dysfunction of the contractile proteins does not contribute to clinical muscle weakness.

Adult↗
PubMed1994

A spin label that binds to myosin heads in muscle fibers with its principal axis parallel to the fiber axis.

We have used an indane-dione spin label (2-[-oxyl-2,2,5,5-tetramethyl-3-pyrrolin-3-yl)methenyl]in dane-1,3-dione), designated InVSL, to study the orientation of myosin heads in bundles of chemically skinned rabbit psoas muscle fibers, with electron paramagnetic resonance (EPR) spectroscopy. After reversible preblocking with 5,5'-dithiobis(2-nitro-benzoic acid) (DTNB), we were able to attach most of the spin label covalently and rigidly to either Cys 707 (SH1) or Cys 697 (SH2) on myosin heads. EPR spectra of labeled fibers contained substantial contributions from both oriented and disordered populations of spin labels. Similar spectra were obtained from fibers decorated with InVSL-labeled myosin heads (subfragment 1), indicating that virtually all the spin labels in labeled fibers are on the myosin head. We specifically labeled SH2 with InVSL after reversible preblocking of the SH1 sites with 1-fluoro-2,4-dinitrobenzene (FDNB), resulting in a spectrum that indicated only disordered spin labels. Therefore, the oriented and disordered populations correspond to labels on SH1 and SH2, respectively. The spectrum of SH2-bound labels was subtracted to produce a spectrum corresponding to SH1-bound labels, which was used for further analysis. For this corrected spectrum, the angle between the fiber axis and the principal axis of the spin label was fitted well by a Gaussian distribution centered at theta o = 11 +/- 1 degree, with a full width at half-maximum of delta theta = 15 +/- 2 degrees. The unique orientation of InVSL, with its principal axis almost parallel to the fiber axis, makes it complementary to spin labels previously studied in this system. This label can provide unambiguous information about axial rotations of myosin heads, since any axial rotation of the head must be reflected in the same axial rotation of the principal axis of the probe, thus changing the hyperfine splitting. Therefore, InVSL-labeled fibers have ideal properties needed for further exploration myosin head orientation and rotational motion in muscle.

Animals↗
PubMed2003

Stretch-induced, steady-state force enhancement in single skeletal muscle fibers exceeds the isometric force at optimum fiber length.

Stretch-induced force enhancement has been observed in a variety of muscle preparations and on structural levels ranging from single fibers to in vivo human muscles. It is a well-accepted property of skeletal muscle. However, the mechanism causing force enhancement has not been elucidated, although the sarcomere-length non-uniformity theory has received wide support. The purpose of this paper was to re-investigate stretch-induced force enhancement in frog single fibers by testing specific hypotheses arising from the sarcomere-length non-uniformity theory. Single fibers dissected from frog tibialis anterior (TA) and lumbricals (n=12 and 22, respectively) were mounted in an experimental chamber with physiological Ringer's solution (pH=7.5) between a force transducer and a servomotor length controller. The tetantic force-length relationship was determined. Isometric reference forces were determined at optimum length (corresponding to the maximal, active, isometric force), and at the initial and final lengths of the stretch experiments. Stretch experiments were performed on the descending limb of the force-length relationship after maximal tetanic force was reached. Stretches of 2.5-10% (TA) and 5-15% lumbricals of fiber length were performed at 0.1-1.5 fiber lengths/s. The stretch-induced, steady-state, active isometric force was always equal or greater than the purely isometric force at the muscle length from which the stretch was initiated. Moreover, for stretches of 5% fiber length or greater, and initiated near the optimum length of the fiber, the stretch-enhanced active force always exceeded the maximal active isometric force at optimum length. Finally, we observed a stretch-induced enhancement of passive force. We conclude from these results that the sarcomere length non-uniformity theory alone cannot explain the observed force enhancement, and that part of the force enhancement is associated with a passive force that is substantially greater after active compared to passive muscle stretch.

Animals↗
PubMed1999

A single-fiber in vitro motility assay. In vitro sliding velocity of F-actin vs. unloaded shortening velocity in skinned muscle fibers.

We describe an approach that allows us to form a micro in vitro motility assay with as little myosin as can be retrieved from a short (approximately 10 mm) segment of a single skinned skeletal muscle fiber (diameter some 100 microm). Myosin is directly extracted from the single fiber segment by a high ionic strength solution in the presence of MgATP, and the extracted myosin is immediately applied to a miniaturized flow cell that has been pretreated with BSA. The observed sliding velocities of fluorescently labeled F-actin are essentially identical with those reported in the literature. Since at the single fiber level most muscle fibers contain only a single myosin heavy chain isoform this approach allows us to determine without additional purification steps, the sliding velocity driven by myosins with different heavy chain isoforms. In addition, this approach can be used to directly correlate under identical experimental conditions unloaded shortening velocity measured in segments of skinned muscle fibers with the in vitro sliding velocity of fluorescently labeled F-actin by extraction of myosin from the same skinned fibers. Such direct correlation was performed with different myosin heavy chain isoforms as well as at different temperatures and ionic strengths. Under all conditions studied, unloaded shortening velocity was 4- to 8-fold faster than sliding velocity in the motility assay even at high temperature (22 degrees C) and ionic strengths >50 mM. This suggests that sliding velocity in the motility assay is limited by additional factors beyond those thought to limit velocity of unloaded shortening in muscle fibers. One such factor might be unspecific ionic interactions between F-actin and the substrate in the motility assay resulting in somewhat higher sensitivity for ionic strength of sliding velocity in the motility assay. This might become of special relevance when using in vitro sliding velocity in assessing functional consequences of mutations involving charged residues of actin or myosin.

Actins↗